1. Field of the Invention
The invention relates in general to the fields of memory cards, and more particularly to a memory card and a method supporting various voltage supplies.
2. Description of the Related Art
Memory cards have been greatly popularized for large capacity, small size and portability characters thereof. Memory cards are applied in many of electronic devices, providing expanded storage for digital cameras, Personal Digital Assistants (PDAs), MP3 players, etc.
One type of conventional memory cards is typically designed to support a single voltage, for example, 3.3 volts. The memory card of this type generally comprises a flash memory storing data and a control chip controlling operations of the flash memory. The control chip is composed of a voltage regulator, a core controller and an output circuit. The core controller is provided for controlling the control chip and operations of other elements in the control chip. The memory card receives an operating voltage supplied from a host. The voltage regulator receives and transforms the operating voltage into a working voltage fed to the core controller. The operating voltage also is fed to the output circuit and the flash memory. The core controller outputs a first control signal to the output circuit, and the output circuit outputs a second control signal to control the flash memory according to the input operating voltage and the first control signal from the core controller.
However, the memory card supporting single power supply may be unintentionally inserted into a computer system that provides a power supply voltages different to the operating voltage, this might cause damages to data store in the memory card and the memory card itself. For solving this problem, another (a second) type of conventional memory cards, which capable of supporting two voltages, are designed. The memory card supporting two voltages is composed of a control chip, a flash memory, an external voltage regulator and an internal voltage regulator disposed on the control chip. The external voltage regulator is provided to transform the operating voltage of, for example, 3.3 or 1.8 volts supplied from the host, into a first working voltage of, for example, 1.8 volts. The first working voltage is supplied to the output circuit, the internal voltage regulator, and the flash memory. The internal voltage regulator further transforms the first working voltage into a second working voltage supplied to the core controller. The output circuit receives the first working voltage and a first control signal from the core controller so as to output a second control signal controlling the flash memory. As the operating voltage from the host is transformed into the first working voltage, which is applicable to the control chip and the flash memory, by the external regulator in advance, the memory card of the this conventional type is capable of supporting two different power supplying. However, the cost of the memory card is increased due to the added external voltage regulator.
For overcome the disadvantage mentioned above, a third type of conventional memory card is provided. Besides the flash memory, the core controller and the output circuit, the memory card of the third type provides only one voltage regulator, which transforms a received operating voltage into a working voltage. The working voltage is supplied to the flash memory and all elements in the control chip, inclusive of the core controller and the output circuit. That is, the voltage regulator in the third type of memory card has to supply working voltages for all of elements in the memory card, so the supplied current is relatively high. However, in view of the high-pressure process, the higher the instantaneous maximum current required, the larger the insulating layer needed. Therefore, in order to provide enough current, the area of the voltage regulator is greatly enlarged, and the cost of the control chip is increased.